Oilsands industry unites to find tailing solutions

Suncor Energy’s new tailings management process looks like a game-changer.

Photograph by: Bruce Edwards, file
, edmontonjournal.com

EDMONTON - While oilsands firms have made significant environmental improvements in recent years — from using less fresh water, emitting less sulphur and reclaiming land into treed hills and meadows — images of huge tailings ponds have tarred the industry.

Because the fine clays — part of the sand, water and residual bitumen mix left after the bitumen is extracted — won’t settle out, companies had to build more and more ponds to contain the backlog.

But recent technological advances, new, tougher standards from the provincial regulator and a decision by the oilsands companies late in 2010 to share existing tailings research, should see an end to most of them within the next few years. Here are some highlights:

Suncor Energy

It’s new tailings management process, called TRO, looks like a game-changer. The liquid tailings are mixed with a binding material and spread over a sloping beach in multiple thin layers.

Suncor plans to spend $1.2 billion over the next couple of years to build and expand the system, which can remove water from the liquid tailings in a matter of weeks. Early success has already enabled Suncor to cancel its plans for five additional tailings ponds, and it will likely reduce the number of ponds at its site from eight to just one as it gets to work on quickly reclaiming its older ponds.

Last September, Suncor marked an industry milestone by becoming the first oilsands company to complete reclamation of a tailings pond, with thousands of trees and bushes planted on the former 220-hectare riverside site formerly known as Pond 1.

The first dike was built in 1967 when Suncor began operations, but the walls were heightened again and again as the tailings refused to settle, leaving the firm with the only one option — to build more and more ponds.

Syncrude

The firm was the first to reclaim dry areas beside mining pits, now home to bison herds, and will soon completely reclaim its first former tailings pond. It is noteworthy that this site will include the first recreated fen — a low, wet area that is biologically rich and common through the boreal area.

Syncrude uses various methods to handle its tailings, including water capping — pumping fresh water to cap a tailings pond and promote settling — and composite tails techniques, which involve adding gypsum to thicken the tailings.

Currently it is putting a big effort into its centrifuge technology, with extensive field tests now complete and commercial-scale implementation on the way. The technology involves putting tailings through spinning vessels which remove the water. The resulting paste is easily handled and quickly reclaimed.

Canadian Natural Resources

CNRL’s Horizon project is the leader in testing carbon dioxide to help settle out the tailings, injecting the liquefied gas into the slurry before the tailings enter the pond where it reacts to form carbonic acid. This reaction changes the acidity of the tailings mixtures and allows the fine clays, silt and sand to settle quickly and leave cleaner water which can be immediately recycled into the bitumen extraction process.

When the new Horizon facility is expanded in the next few years, another new treatment will be added. Spinning chambers will remove water from the coarse sand, and thickeners will remove the water from the fine clays, silts and sand. These dewatered tailings streams will then be combined with waste CO2 from the plant. More water will be released when the tailings are deposited, and the CO2 will react chemically to form mineral carbonates, basically sedimentary rock.

Shell Energy

Since 2006, Shell has been working on a technology that involves collecting fine tailings from a discharge pond and adding chemicals to accelerate de-watering, a system called atmospheric fines drying (AFD). The material is then placed on a sloping surface to enhance further drying by evaporation. The 300-square-metre test area will contain 250,000 tonnes of sand and clay by the end of the year. A second, larger test area will open this year.

Titanium Corp.

The Edmonton-based firm sees rare minerals like zircon and titanium, as well as bitumen and solvents, in tailings. Its technology, run recently in a pilot project at the federal CanmetENERGY in Devon, proved a success. The firm aims to partner with Suncor, Syncrude or Canadian Natural Resources this year to build a commercial-sized, stand-alone project.

Titanium’s technology works on the froth tailings — the most concentrated stream of the two tailings streams that pour into the ponds. And its current system works only with naphtha-based processes used by Syncrude, Suncor and CNRL. A second system, designed to work with the paraffinic tailings produced by Shell and Imperial’s Kearl, is in early tests.

Titanium estimates it can recover 400,000 barrels of solvent (which now evaporates from the ponds) and up to three million barrels of bitumen at each plant every year, which means extra output for the plant — and extra royalties for Alberta.

A separate mineral recovery plant using equipment from the mining industry would handle the coarse, mineral-rich sands.

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